Various forms of test elements for glucose determinations have been put into practice for sample application relative to a flat, rectangular strip geometry, especially so-called top-dosing test strips (i.e., application of a body fluid sample such as blood from above onto a test field that is mounted in a planar manner between both narrow sides of the measurement device).
In optical systems, a test field on a test strip can be measured through a hole in a carrier foil by means of absorption photometry measured in reflection. In general, the test strip is positioned above an optical measuring unit of the device, and a body fluid sample is applied to the test strip.
With top-dosing systems, the test strip is positioned in the middle of a housing trough to load it with the body fluid sample, and thus within the contour of the device. A user must place the body fluid sample from, for example, a finger onto the test strip in the middle of the device. In doing so, the user may have difficulty in seeing the target site behind the finger. Likewise, the body fluid sample may run onto the device or may even run onto or into the opening to the optical measuring unit, especially when a relatively large amount of sample hangs on the finger. Therefore, inaccurate application or excessive amounts of sample can contaminate the trough of the test strip holder or the optical measuring unit.
With outside-dosing systems, the test strip is removed, the body fluid sample is applied outside the device, and the test strip then is inserted back into the device. As with top-dosing systems, surfaces in outside-dosing systems may become contaminated because the complete test strip area can be used for sample application. In addition, the underside of the test strip can become unintentionally contaminated when, for example, the test strip is placed on a contaminated surface for sample application. Such contaminations can result in an erroneous measurement.
With out-of-meter-dosing systems, the body fluid sample is transported to the site of measurement through capillaries of the test strip. The required amount of body fluid sample, however, is considerably larger than with methods in which the sample is directly applied to the test field because firstly the capillaries have to be filled with sample. This disadvantage can be avoided with electrochemical test strips in which measurements can be carried out using common sample volumes by guiding the electrodes to the outside. However, the manufacture of such capillary test strips is relatively complicated due to the elaborate assembly process. Likewise, costs are proportionately high due to the high material costs for the bottom and cover foil.
For the foregoing reasons, there is a need for additional devices and systems for body fluid analysis having improved body fluid sample application characteristics and that avoid contamination.